The basic principle is that in order to conceive a girl, you have sex 2-3 days before the predicted day of ovulation and then stop. To conceive a boy, you have sex on the day of ovulation.

There's a book or two on the subject.

We inadvertantly used the 'method' and it fits that we're having a little girl!

Oh, also...he recommends certain positions to help specific sperm travel better, too, enabling the gender you are hoping for. He also specifys whether or not the wife should have an orgasm to facillitate semen..............this is all info available online, if you don't want to read the book. I was interested after we conceived so I went to go find out about it.

The theory uses the observed data that "male" sperm travel faster but die sooner while "female" sperm are slow swimmers but live longer.

So, if you time intercourse at the beginning of your mucus observations, the girl sperm will likely be the only living sperm when the egg is released. If you time intercourse close to ovluation, the boys will beat the girls to the egg.

It's no guarantee of course, because there is great variation from person to person.... but it does improve the chances based on the data.

__________________Pax, ke

ke's universal disclaimer: In my posts, when I post about marriage, canon law, or sacraments I am talking about Latin Rite only, not the Orthodox and Eastern Rites. These are exceptions that confuse the issue and I am not talking about those.

I know of people who swear by this method. In my personal experience, conception once occured so early in the cycle, it should have been impossible to begin with. We did not get a girl. We got boys... two of them! All I can say is, God must really want us to have lots of boys!

We have two children so far -- one boy, one girl -- and the Shettles technique inadvertently "worked" with both. At the time, I was just keeping track of my cycles for medical reasons; we weren't "using NFP" to influence the odds of conception, let alone gender. But it was interesting to be look back, in hindsight, and figure out what happened.

It seems to me that, if this technique is reasonably accurate, it raises some moral concerns. In our marriage preparation class, the people who gave the NFP talk went into a lot of "Rah-Rah!" detail about gender prediction as an "amazing bonus feature!!!," but they didn't even suggest that it could be used for selfish reasons. I even asked specifically about this (trouble-maker that I am... ), and they gave a vague answer about how the method "wasn't totally accurate anyway" -- which, while true, is sort of beside the point when it comes to determining the morality of one's intent. It seems like they could at least have suggested that couples consult a priest on this matter, if they had any doubts.

For example, what if a couple decided that they wanted to have a child of a certain gender, because they didn't want to have to redecorate the nursery? (I know, that sounds ridiculous... but the way children are viewed these days, I wouldn't be surprised. )

[T]he Couple-To-Couple League responds correctly to the question with some hesitation because too much concern about “sex selection” can detract from seeing the child as a “gift” and lead instead to seeing the child as a “product” or “construction.” This concern and deficit is a valid one, cf. Donum Vitae (1987) and Evangelium Vitae (1994) nn. 22, 39, 63 et passim.